program Camping;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  n,i,x: integer;
begin
  x:=0;
  readln(n);
  if (n mod 2=0) then
    for i:=1 to (n div 2) do
      x:=x+i*2
  else
    for i:=1 to (n div 2) do
      x:=x+i*2+1;
  writeln(x);
  readln;    
  { TODO -oUser -cConsole Main : Insert code here }
end.
 